Test Description
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers on the diagnostic table.
- 4: Verifies that the body control module (BCM) is providing ground to the horn relay.
- 5: Tests for voltage at the battery positive voltage terminal of the horn relay coil.
- 7: Tests for voltage at the battery positive voltage terminal of the horn relay switch. The HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.
- 15: The horns need maximum current flow to operate properly. A high resistance (greater than 0.5 ohms) in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Check the circuits for faults that would restrict current flow.
- 17: The horn relay control circuit includes the horn switch. The horn switch is part of the inflatable restraint steering wheel module. The horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit.
Horns Inoperative Diagnostic Table
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check-Horns? | Go to Step 2 | Go to Diagnostic System Check - Horns |
| 2 | Depress the horn switch. Do the horns operate? |
Go to Step 3 | Go to Step 5 |
| 3 |
|
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 4 |
| 4 | Test the BCM portion of the horn relay control circuit for a high resistance or an open. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 13 |
| 5 |
|
Go to Step 6 | Go to Step 16 |
| 6 |
|
Go to Step 7 | Go to Step 17 |
| 7 | Connect a test lamp between the battery positive voltage circuit of the horn relay switch and a good ground. Does the test lamp illuminate? |
Go to Step 8 | Go to Step 18 |
| 8 | Momentarily connect a 15-amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the horn control circuit. Do the horns operate? |
Go to Step 14 | Go to Step 9 |
| 9 |
|
Go to Step 10 | Go to Step 19 |
| 10 |
|
Go to Step 11 | Go to Step 20 |
| 11 | Inspect for poor connections at the harness connector of the horn. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 12 |
| 12 |
|
Go to Step 15 | Go to Step 23 |
| 13 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 21 |
| 14 | Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 24 | Go to Step 22 |
| 15 | Repair the high resistance in the horn control circuit or the horn ground circuit. Refer to Circuit Testing
and to Wiring Repairs
in Wiring Systems. Did you complete the repair? |
Go to Step 24 | - |
| 16 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you complete the repair? |
Go to Step 24 | - |
| 17 |
IMPORTANT:
The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement
in SIR. To disable the SIR system refer to SIR Disabling and Enabling Zone 3
in SIR.Repair the open or short to voltage in the horn relay control circuit. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems.Did you complete the repair? |
Go to Step 24 | - |
| 18 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you complete the repair? |
Go to Step 24 | - |
| 19 | Repair the open or high resistance in the horn control circuit. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you complete the repair? |
Go to Step 24 | - |
| 20 | Repair the open or high resistance in the horn ground circuit. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you complete the repair? |
Go to Step 24 | - |
| 21 |
IMPORTANT:
Perform the BCM procedure when replacing the BCM. Replace the BCM. Refer to Body Control Module Replacement
in Body Control Systems.Did you complete the repair? |
Go to Step 24 | - |
| 22 | Replace the horn relay. Refer to Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness)
. Did you complete the replacement? |
Go to Step 24 | - |
| 23 | Replace the horns. Refer to Horn Replacement . Did you complete the replacement? |
Go to Step 24 | - |
| 24 | Operate the horns. Do the horns operate properly? |
System OK | Go to Step 1 |